[PATCH 4.19 31/48] block, bfq: protect bfqd->queued by bfqd->lock

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Yu Kuai <yukuai3@huawei.com>

commit 181490d5321806e537dc5386db5ea640b826bf78 upstream.

If bfq_schedule_dispatch() is called from bfq_idle_slice_timer_body(),
then 'bfqd->queued' is read without holding 'bfqd->lock'. This is
wrong since it can be wrote concurrently.

Fix the problem by holding 'bfqd->lock' in such case.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220513023507.2625717-2-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Khazhy Kumykov <khazhy@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 block/bfq-iosched.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -416,6 +416,8 @@ static struct bfq_io_cq *bfq_bic_lookup(
  */
 void bfq_schedule_dispatch(struct bfq_data *bfqd)
 {
+	lockdep_assert_held(&bfqd->lock);
+
 	if (bfqd->queued != 0) {
 		bfq_log(bfqd, "schedule dispatch");
 		blk_mq_run_hw_queues(bfqd->queue, true);
@@ -5278,8 +5280,8 @@ bfq_idle_slice_timer_body(struct bfq_dat
 	bfq_bfqq_expire(bfqd, bfqq, true, reason);
 
 schedule_dispatch:
-	spin_unlock_irqrestore(&bfqd->lock, flags);
 	bfq_schedule_dispatch(bfqd);
+	spin_unlock_irqrestore(&bfqd->lock, flags);
 }
 
 /*